1. Field of the invention
The present invention relates to producing and/or treating a moving, material web, and, more particularly to pressing two axially parallel rolls against each other in a device for producing and/or treating a moving material web.
2. Description of the Related Art
Pairs of rolls are often used in machines on which paper, board or other material webs are produced or treated. By way of such pairs of rolls, material webs are, for example, calendered, coated or printed. Here, great attention is regularly paid to the pressing force transmitted between the rolls of the pair. Maintaining a specific pressing force is usually of critical importance for the result of the treatment of the material web, be it, for example, the calendering result in the calender or the coating result when applying a size or a pigment-containing coating color.
EP 0 978 589 A2 discloses registering the pressing force transmitted between a pair of rolls and, in particular, its axial distribution, by way of sensors which are embedded into one of the rolls close to the surface, specifically in the shell of the roll or in a cover fitted to the shell. Although the line pressure between the rolls can be registered very accurately in this way and, in the event of deviations from the desired values, appropriate activation of suitable force devices can be carried out in order to effect more intense or less intense pressing of the rolls, embedding the sensors in the roll body admittedly has the disadvantage that this makes the production of the roll more difficult and more expensive. In addition, it is necessary to take into account that, from time to time, grinding of the outer functional layer of the roll can be necessary in order to rectify damage in the roll surface. If the sensors are arranged close to this functional layer or even embedded in the latter, this can result in the outer layer of the roll being available for the grinding only over a small part of its thickness and replacement of the roll can be required correspondingly early.